1. Technical Field
The present invention generally relates to cellular mobile communication systems and, in particular, to Quality of Service (QoS) negotiations between an intermediate node and secondary nodes.
2. Description of the Related Art
Each of the secondary nodes in a General Packet Radio Service (GPRS) network may have their own QoS provisioning constraints (e.g., limited air interface capacity/capability). Thus, a problem arises as to how an intermediate (middle) node (e.g., the Serving GPRS Support Node (SGSN)) in the GPRS network should go about determining a suitable End-to-End (E2E) Quality of Service (QoS) contract, when that contract has to be negotiated with two or more secondary nodes. For example, the secondary nodes may include a Gateway GPRS Support Node (GGSN) and a packet control unit (PCU). In addition, the contract may have to be dynamically updated based on current network and user capabilities.
When a QoS contract is negotiated across multiple nodes, each node generally records the negotiated QoS. More specifically, the negotiated QoS parameters per connection may be recorded. This may reduce the negotiation time in case the same E2E connection is re-established in the future, such as after the original transfer has been completed or if the connection fails midway through. A reduced negotiation time may be achieved if the recorded QoS profile can be used for the connection or used as a basis for such connection.
This brings a challenge to node negotiations relating to a QoS profile, since the currently recorded QoS profile parameters may be out-of-date. In a GPRS network, the original QoS profile will be recorded and then generally deleted in the secondary node (specifically the PCU within the Base Station Subsystem (BSS)) after a Packet Flow Context (PFC) timer has expired. The PFC is the method through which the SGSN is able to provide the BSS with information relating to the ongoing user data transmission, including the QoS profile of that transmission. A currently recorded QoS profile may provide downgraded services compared to the originally requested QoS profile. Therefore, it is possible at the time of a subsequent request that the conditions have changed such that the QoS afforded by the originally requested QoS profile could now be supported. In order to provide the mobile device with the original QoS afforded by the originally requested QoS profile, the new request by the intermediate node (i.e., the SGSN) would need to include the originally requested QoS. In the case of GPRS, the SGSN should include the originally requested QoS profile in the “Download-BSS-PFC” message. This would allow the secondary node (e.g., PCU) to fully offer the resources currently available. Nonetheless, such a procedure would potentially increase the QoS negotiation times back to their original levels, removing the benefits of the secondary node recording the previous QoS profile.
FIG. 1 is a general flow diagram of a conventional implementation of a GPRS Create-BSS-PFC procedure 100 after a Download-BSS-PFC request message. A problem with the current GPRS Create-BSS-PFC procedure 100 is that the procedure does not specify which QoS contract an intermediate node (i.e., the SGSN) 104 should include in the Create-BSS-PFC-Req message conveyed from the intermediate node 104 to a secondary node, e.g., the Base Station Subsystem (BSS), 102. The Create-BSS-PFC-Req message may be followed by a Create-BSS-PFC-Accept message from the BSS 102 to the SGSN 104.
A further problem is that normally the SGSN uses the currently negotiated QoS contract and not the original QoS requested by the mobile/network. The intermediate node can effectively prevent the secondary node from increasing the offered QoS by imposing an already downgraded QoS profile. In that case, the PCU can not upgrade the QoS (by modifying the BSS-PFC procedure 100) towards the originally requested QoS profile. As a result, resources are not used efficiently and therefore the customer's E2E QoS experience also is not optimized.